Overheating of this kind can occur during operation of the engine under high load, especially during full-load operation, because of so-called knocking combustions. In this context, it is known, for example, to detect the full-load state via the fully opened throttle flap with a throttle flap switch and to shift the composition of the air/fuel mixture supplied to the engine toward the fuel-rich end. The enrichment is characterized also as full-load enrichment. With this enrichment, the tendency of the mixture to cause knocking is reduced. An excessive development of heat associated with knocking combustions can be avoided in this manner.
In the event that this protective measure fails, comparatively costly damage to the engine or to the catalytic converter in the exhaust gas of the engine occurs. For this reason, there is an interest to be able to monitor the operation of this protective arrangement.